Jessica Murphy, Parliamentary Bureau

OTTAWA - Prime Minister Stephen Harper says the world is watching to see whether Iran will spare the noose for a Canadian citizen convicted of espionage.

On Monday, Harper weighed in on the incarceration of Hamid Ghassemi-Shall, saying Canadian officials have been working "for some time" on his case.

"The government of Iran should know the whole world will be watching and they will cast judgment if terrible and inappropriate things are done in this case," he told reporters.

In a statement released late Sunday, Foreign Affairs urged clemency on compassionate and humanitarian grounds for Ghassemi-Shall, who they believe is at imminent risk of execution.

Ghassemi-Shall was arrested in Iran in 2008 while visiting relatives and accused and subsequently convicted of espionage.

The Toronto man, who holds dual Iranian and Canadian passport, has been held in Tehran's notorious Evin prison since, the same jail where Canadian photographer Zahra Kazemi was raped and murdered in 2003.

The relationship between Canada and Iran is strained and Tehran doesn't recognize dual citizenship.

Gloria Nafziger, with Amnesty International, said Monday it's still unclear why Ghassemi-Shall was arrested in the first place and what evidence the regime used against him.

"One of the main concerns is he hasn't had a fair trial and he has received a death sentence," she said.

She also said there has been reports he has been treated "harshly" during his four years of captivity.

"The word Evin and torture are essentially synonymous," she said.

Nafziger urged Canadians to continue to write to Iran to appeal to remove him from death row.